1. Field of the Invention
The present invention relates to a substrate processing apparatus for applying a uniform surface treatment on a substrate of a large area, and an apparatus for processing an electron source substrate, utilizing such substrate processing apparatus.
2. Description of the Related Art
There is already known a display panel of an image forming apparatus, utilizing a phenomenon of electron emission from a thin film, formed on a substrate by an electron source producing apparatus, by an electric current flown parallel to the film surface, and formed by combining such electron source and a phosphorescent material. Such electron emitting device generally includes two types, namely a thermal electron emitting device and a cold cathode electron emitting device. Also the cold cathode electron emitting device includes a field emission type (hereinafter referred to as FE type), a type having a metal/insulator/metal structure ((hereinafter referred to as MIM type), and a surface conduction electron emitting device.
The surface conduction electron emitting device utilizes a phenomenon of electron emission by supplying a thin film of a small area, formed on a substrate, with a current parallel to the film surface. Basic structure and producing methods thereof are disclosed, for example, in Japanese Patent Application Laid-open Nos. H07-235255 and H08-171849. A typical structure of the surface conduction electron emitting device is as follows. An electroconductive film for forming an electron emitting part, provided so as to connect a pair of device electrodes on a substrate, is subjected to an electrical energization, called a forming, and then to an activation process, thereby forming an electron emitting part.
The forming is a process of applying a voltage between the ends of the electroconductive film for forming the electron emitting part, to locally cause a destruction, a deformation or a modification in the electrocondutive film, thereby forming a fissure (gap) having a state of an electrically high resistance.
The activation is a process of applying a voltage between the ends of the electroconductive film under a reduced-pressure atmosphere containing an organic compound thereby forming a carbon film in the vicinity of the fissure. The electron emission is executed from the vicinity of the fissure.
The surface conduction electron emitting device, being simple in structure and easy to manufacture, has an advantage that a multitude of elements can be arrayed over a large area, and is utilized in an electrically charge beam source and in an image forming apparatus such as a display apparatus.
In a prior producing method for a surface conduction electron emitting device, a device bearing a pair of device electrodes and an electroconductive film is placed under a reduced-pressure atmosphere and is subjected to a forming process thereby forming a fissure in the electroconductive film. Thereafter, an activation process is executed by introducing a gas of an organic compound into the reduced-pressure atmosphere and applying a suitably selected pulsed voltage for a period of from several minutes to several tends of minutes to deposit carbon or a carbon compound in the vicinity of the fissure thereby forming a carbon film. Such activation process is effective for improving the characteristics of the device. Through such activation process, the property of the electron emitting device, namely an electron emission current Ie, is improved showing a significant increase, while maintaining a threshold voltage.
However, such activation process involves following limitations.
The activation process, for depositing carbon or a carbon compound on the electron emitting part and the vicinity thereof, is executed by decomposing an organic compound which is adsorbed onto the device substrate from the atmosphere. Therefore, when a number of the devices subjected simultaneously to the activation process increases, an amount of the organic compound, that is decomposed and consumed on the electron source substrate per unit time also increases. As a result, there may be induced a fluctuation of the concentration of the organic compound in the atmosphere, a slower formation rate of the carbon film and a fluctuation in the carbon film depending on a position within the electron source substrate, thus leading to a deteriorated uniformity of the electron source.